The present invention relates to mechanical couplings for transmitting torque between an engine and a generator/starter, and methods for using the same.
Gas turbine engines can include an integrated drive generator that converts mechanical energy from the gas turbine engine into electrical energy. When beginning in a stopped condition, gas turbine engines must generally reach a given operating speed before they are capable of self-sustained operation. Typically, gas turbine engines are started using a pneumatic starting mechanism, or by diverting power from another engine that is already operational. Such devices provide external power to the gas turbine engine, but can add weight and complexity, which is undesirable for many applications, such as aerospace applications.
It is desired to use a generator as a starter, to provide external power to a gas turbine engine to reach self-sustaining operation. Generators can be operated as electric motors (i.e., starters) by supplying electrical energy to its windings in a well-known manner. However, what may appear to be a simple matter of operating the generator as a motor to start the gas turbine engine is complicated by the presence of other devices engaged with drive shafting between the gas turbine engine and the generator/starter. For instance, a differential typically links the gas turbine engine and the generator/starter, and various pumps, hydraulic units and other equipment are engaged to the differential. Operation of the generator/starter as an electric motor is inhibited by the presence of the equipment engaged to the differential, which can cause the differential to undesirably divert torque produced by generator/starter to accessories like the hydraulic units rather than to the gas turbine engine. This represents an obstacle to using a generator as a starter for a gas turbine engine.